Cells which are the smallest unit of the human body maintain the balance of cell number by cell division upon intracellular regulatory functions, cell growth, and cell death and disappear, when cells are normal. If the cells are damaged by any cause, cells may be recovered by treatment to thereby serve as normal cells. However, if cells are not recovered, cells die by themselves. A condition in which abnormal cells that do not control proliferation and inhibition thereof for a variety of reasons are excessively proliferated and also cause tumefaction and destruction of normal tissues by invading surrounding tissues and organs is defined as cancer. As such, cancer refers to cell proliferation that is not inhibited, and cancer destroys the structure and function of normal cells and organs. In this regard, it is significantly important to diagnose and treat cancer.
However, there are problems during treatment in which treatment cases of respective patients differ due to different therapeutic responses resulting from genetic differences in the individual patients having cancer. Thus, in order to effectively treat cancer patients, it is required to develop a functional targeting agent capable of targeting tumor microenvironment, which depends on radioresponsiveness, and a biomarker. Accordingly, it is possible to establish personalized diagnosis and treatment for individual patients.
In addition, drug delivery systems or targeted therapies that selectively deliver drugs to cancer cells and cancer tissues are technologies that have received much attention, because even if the same amount of an anticancer agent is used, drug efficacy may be increased while side effects of drugs on normal tissues may be significantly reduced at the same time. In addition, when such technologies are applied to gene therapy, selective delivery of virus to cancer cells can increase treatment efficacy and reduce severe side effects. For this purpose, antigens that are mainly specific to tumor cells and antibodies that target such antigens have been developed up to date. However, in the case of antibodies, there are problems including concerns of immune response and low efficiency of penetration into tissues. In the case of peptides, a molecular weight thereof is so small that there is less concern of an immune responses and the penetration of peptides into tissues is easy. Therefore, if cancer-targeting peptides are coupled with existing anticancer drugs, such resulting products can be utilized as intelligent drug vehicles that selectively deliver drugs to tumors.